integrations: Round top borders and remove box shadow.
integrations: Round top borders and remove box shadow.

This makes it look good with the new footer.

andersk/zulip,andersk/zulip,andersk/zulip,andersk/zulip,zulip/zulip,rht/zulip,zulip/zulip,andersk/zulip,rht/zulip,rht/zulip,rht/zulip,andersk/zulip,andersk/zulip,zulip/zulip,zulip/zulip,zulip/zulip,zulip/zulip,rht/zulip,rht/zulip,rht/zulip,zulip/zulip